Acute diarrhea is still one of the main causes of disease in developing countries. At the National Reference Laboratory for Acute Diarrhoeal Diseases, of the "Pedro Kourí" Tropical Medicine Institute, 54 Plesiomonas shigelloides strains were serotyped. As a result, the circulation of four new serotypes (O20:H2, 056:H18, 071 :H31,081 :H22) was detected. The most common antigenic variant was 094:H3. In addition, the susceptibility pattern to 21 antimicrobial agents (AA) was studied. Highest percentages of resistance were observed to ampicillin (77.7%), tetracycline (29.2%), and erythromycin (18.5%) while, to all other AA the resistance percentages were under 33%. There was no evidence of association between the serotypes and the multi-resistance patterns present in the strains under study. The frequency of virulence factors was determined: 21.15% of the strains turned out to be ß-haemolytic; 73.7% showed the presence of biofilm and 92.31% were hydrophobic. In 17.3% of the strains, the three virulence factors analysed were present. When establishing the relationship among the different virulence factors and the serotypes of the strains through cross reaction with the Shigella genus, there was evidence that 93.3% of the strains showed at least one of the virulence factors studied. Likewise, at least one of the virulence factors analysed was present in 90.9% of the multi-resistant strains.